If you don't like creating Regular Expression patterns, here is a trick so you can easily find and extract text:
$text = 'The problem was discussed in KB552356. Mail feedback to tobias @powershell.com' $words = $text -split ' ' $words -like 'KB*' KB552356 $words -like '*@*.*' email@example.com
By splitting the text into words, you can then use -like and simple patterns that use the "*" wildcard.